Thanks Voidlord
I did as you advised and got an Opal coin message stating that
wallet.dat corrupt, salvage failed
So clicked on the copy I had made of the waller.dat and tried again
This time the wallet opened and started syncing but then I got the same messages as described in my previous post, i.e.
This application has requested the runtime to terminate it in an unusual way. Please contact the application's support team for more information.
Followed by this:
Opal-Qt.exe has stopped working
A problem caused the program to stop working correctly. Windows will close the program and notify you if a solution is available.
I'm assuming (in the absence of any other info) that the problem somehow relates to the fact that the following file (which is part of C++ 2012 (x86 and x64)
http://www.microsoft.com/en-us/download/details.aspx?id=30679) can't be run because, despite meeting the system requirements of this file, my Windows 7 service pack 1 OS doesn't see this file as a valid Win 32 application
http://download.microsoft.com/download/1/6/B/16B06F60-3B20-4FF2-B699-5E9B7962F9AE/VSU4/vcredist_arm.exeI've tried d/loading the file (vcredist_arm.exe) from an alternative m/soft site - same result
If anyone-else has had the same problem with this file and found a solution, please post.
If not, I think maybe I should now just wait until the new wallet version is launched and use that (always assuming of course that the same problem doesn't arise)- in the meantime keeping my modest stash of opal on my bittrex a/c and hope for the best

In the meantime thanks again for your help so far.